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Overview of Cranial Nerves Functions

May 7, 2025

Overview of Cranial Nerves

This lecture provides a comprehensive overview of the cranial nerves, summarizing their origins, structures supplied, fiber types, functions, and passage through the skull. This serves as a recap of detailed individual discussions on each nerve.

Breakdown by Nerve

1. Olfactory Nerve (CN I)

  • Origin: Nasal cavity (roof, olfactory mucosa)
  • Structures Supplied: Nasal cavity
  • Fibers: Special Visceral Afferent (SVA) fibers
  • Function: Smell (olfaction)
  • Sensory/Motor/Both: Sensory
  • Skull Passage: Olfactory foramen of cribriform plate (Ethmoid bone)

2. Optic Nerve (CN II)

  • Origin: Retina
  • Structures Supplied: Photoreceptors (rods, cones, ganglion cells)
  • Fibers: Special Sensory Afferent (SSA) fibers
  • Function: Vision
  • Sensory/Motor/Both: Sensory
  • Skull Passage: Optic canal

3. Oculomotor Nerve (CN III)

  • Origin: Midbrain
  • Structures Supplied: Superior rectus, levator palpebrae superioris, inferior rectus, inferior oblique, medial rectus, pupil (sphincter pupillae), ciliary muscle
  • Fibers: General Somatic Efferent (GSE), General Visceral Efferent (GVE)
  • Function: Eye and eyelid movement, pupil constriction, accommodation
  • Sensory/Motor/Both: Motor
  • Skull Passage: Superior orbital fissure

4. Trochlear Nerve (CN IV)

  • Origin: Midbrain (inferior colliculus)
  • Structures Supplied: Superior oblique muscle
  • Fibers: General Somatic Efferent (GSE)
  • Function: Eye movement (depression and lateral rotation)
  • Sensory/Motor/Both: Motor
  • Skull Passage: Superior orbital fissure

5. Trigeminal Nerve (CN V)

  • Origin: Pons, trigeminal ganglion
  • Structures Supplied: Facial skin, mucous membranes, muscles of mastication, tensor tympani, tensor veli palatini
  • Fibers: Special Visceral Efferent (SVE), General Somatic Afferent (GSA)
  • Function: Sensory from face, mastication
  • Sensory/Motor/Both: Both
  • Skull Passages: Superior orbital fissure (V1), Foramen rotundum (V2), Foramen ovale (V3)

6. Abducens Nerve (CN VI)

  • Origin: Pons
  • Structures Supplied: Lateral rectus muscle
  • Fibers: General Somatic Efferent (GSE)
  • Function: Eye movement (abduction)
  • Sensory/Motor/Both: Motor
  • Skull Passage: Superior orbital fissure

7. Facial Nerve (CN VII)

  • Origin: Pons
  • Structures Supplied: Muscles of facial expression, stapedius, lacrimal/nasal/Palatine glands, anterior 2/3 of tongue for taste
  • Fibers: Special Visceral Efferent (SVE), General Visceral Efferent (GVE), Special Visceral Afferent (SVA), General Somatic Afferent (GSA)
  • Function: Facial expression, secretion, taste
  • Sensory/Motor/Both: Both
  • Skull Passages: Internal acoustic meatus, stylomastoid foramen

8. Vestibulocochlear Nerve (CN VIII)

  • Origin: Pons-medulla junction
  • Structures Supplied: Vestibule, semicircular canals, cochlea
  • Fibers: Special Sensory Afferent (SSA)
  • Function: Balance (static and dynamic equilibrium), hearing
  • Sensory/Motor/Both: Primarily Sensory (with minor efferent modulation)
  • Skull Passage: Internal acoustic meatus

9. Glossopharyngeal Nerve (CN IX)

  • Origin: Medulla
  • Structures Supplied: Stylopharyngeus, pharynx, tongue, tonsils, ear
  • Fibers: Various including SVE, GVA, GSA, GVE
  • Function: Taste, swallowing, salivation
  • Sensory/Motor/Both: Both
  • Skull Passage: Jugular foramen

10. Vagus Nerve (CN X)

  • Origin: Medulla
  • Structures Supplied: Pharynx, larynx, heart, lungs, abdominal viscera
  • Fibers: GVE, SVA, GSA, SVE, GVA
  • Function: Parasympathetic regulation
  • Sensory/Motor/Both: Both
  • Skull Passage: Jugular foramen

11. Accessory Nerve (CN XI)

  • Origin: Medulla, cervical spinal cord
  • Structures Supplied: Sternocleidomastoid, trapezius
  • Fibers: GSE, SVE
  • Function: Neck and shoulder movement
  • Sensory/Motor/Both: Motor
  • Skull Passage: Jugular foramen, foramen magnum

12. Hypoglossal Nerve (CN XII)

  • Origin: Medulla
  • Structures Supplied: Intrinsic and extrinsic muscles of the tongue
  • Fibers: General Somatic Efferent (GSE)
  • Function: Tongue movement
  • Sensory/Motor/Both: Motor
  • Skull Passage: Hypoglossal canal

Conclusion

This lecture emphasizes the complexities and vital functions of cranial nerves, highlighting their diverse roles in sensory perception, motor control, and autonomic regulation.

Full transcript